Method for fireproofing cellulosic materials



United States Patent i 2,994,620 METHOD FOR FIREPROOFING CELLULOSICMATERIALS Jean-Jacques Franck, Neuilly-sur-Seine, and Basile Sandor,Paris, France, assignors to Ignicel Societe Anonyme, Paris, France, acorporation 'of France No Drawing. Filed Nov. 6, 1957, Ser. No. 694,706Claims priority, application France Nov. 6, 1956 11 Claims. (Cl. 117137)The present invention relates to a method for the fireproofing ofcellulosic materials.

The materials which may be treated according to the invention includetimber, wood for making furniture, plywood, ligno-cellulosic fibers orparticles, or agglomerates thereof such as heat and sound-insulatingpanels.

It is known that certain ammonium salts and more particularly ammoniumphosphates can be used for modifying the inflammability of cellulosicmaterials impregnated therewith. The materials thus treated, whensubmitted to the action of a high temperature, undergo a fiamelesscarbonization and produce a carbonaceous mass without ignition of theevolved gases, thus avoiding the origination or propagation of a fire.

However, it has not been possible to generalize the use of such salts,and particularly the use of ammonium phosphates, as would have beendesirable. The impregnation treatments as presently used are difficultto apply because they require either an expensive apparatus for carryingout the impregnation under pressure, or an impregnation by prolongedimmersion, with a very low efiiciency in use of equipment. Moreover, theammonium phosphates constitute a nutrient medium for the microorganismswhich attack the wood and this may have an unfavorable influence onmetal parts which come into contact with the treated materials.

On the other hand, it has been found that certain waterproofedligno-cellulosic agglomerates may, when submitted to a fireproofingtreatment, become non-inflammable but that, if no particular precautionsare taken, the said treatment modifies certain of the characteristicfeatures of the said agglomerates and, more particularly, theirsensitiveness to humidity, which is substantially increased.

In order to take advantage of the fireproofing properties of ammoniumphosphates, a commercial fireproofing method for cellulosic orligno-cellulosic materials, must therefore, in any case:

(a) Cause a quantity of ammonium phosphate which is sufiicient to obtainthe fireproofing to penetrate the material in a reasonable time;

(b) Avoid conferring to the treated materials an attacking action onmetallic parts driven therein or brought into contact therewith;

(c) Protect the materials from the micro-organisms promoted by thepresence of ammonium phosphates, such a protection being eventuallyobtained by conferring to said materials particular properties inaddition to fireproofing and/or waterproofing;

(d) Cause no modification of the mechanical and surface properties ofthe treated materials;

(e) Avoid influencing unfavorably the prior or subsequent waterproofingof the treated materials.

It has been found that the above conditions could be satisfied byforming the waterproofing salts in situ in such a manner that for agiven period of soaking or other treatment, the quantity of saltretained in the treated cellulosic or ligno-cellulosic material, isconsiderably increased.

It has furthermore been found that the said formation in situ of thewaterproofing salts may, in certain cases,

e still further increased when the material which is to be Patented Aug.1, 1961 fireproofed has a sufiieient degree of humidity and, moreparticularly, when the said material is submitted to a prior treatmentcausing a dilatation of the fibers. In the latter case, it has beenfound that the best results were obtained When the said treatment issuch that it cooperates in the formation of the waterproofing salt.

A simplified flow diagram of an illustrative manner of practicing theinvention when fireproofing insulating boards is as follows:

The fireproofing method according to the invention consists inincorporating in the material at least one fireproofing salt such as anammonium hydrogen phosphate i.e. monoor diammonium phosphates orcompounds capable of forming such a salt while simultaneously causingammonium phosphates to be formed and retained in situ in sufiicientquantity without altering the mechanical and surface properties of thetreated material.

The introduction of the waterproofing salts or components thereof may becarried out by immersion, sprinkling, atomizing, aspiration in vacuumvats or the like.

Prior to the introduction of the waterproofing compounds, it may beadvantageous, more particularly for cellulosic materials, to cause thechannels and cells in the said material to expand, such an expansionbeing obtained without alteration of the fibers by soaking the materialin a solution of ammonia having a concentration comprised between about3% and 10% according to the nature of the material. The immersion timeof the material in the said solution as well as the concentrationthereof, is determined in such a manner as to avoid an alteration of thefibers while expanding the channels, then the cells of the mass, tocause a penetration of ammonia therein, which makes possible thereaftera rapid penetration of a suflicient quantity of P0 ions which, bycombination with the ammonia from the expanding solution will form insitu the waterproofing ammonium phosphates. When the material is firstexpanded the second bath furnishing P0 ions preferably consists of anaqueous solution of ammonium hydrogen phosphate PO (NH H wherein m and nare l-Z and m+n=3, having a concentration comprised between about 10 and30% and pH comprised between 3 and 7 preferably between 3.9 and 6.2according to the nature of the treated material. The pH of the phosphatesolution determines that of the fireproofed material after treatment andconsequently the activity or neutrality i.e. the degree of attack of thematerial on metal parts which will thereafter come into contacttherewith. The above mentioned pH limits 3.9 and 6.2 for the phosphatesolution correspond for wood fireproofed according to the invention, topH values comprised between 6.3 and 7.4. The wood will have no attackingaction on metal parts if the pH of said wood is at least equal to thatat which ion phosphate precipitates, but too high a pH leads to adissociation of the ammonium phosphate.

When it is desired to fireproof a ligno-cellulosic mate rial such asagglomerates or particles of fibers for the formation of agglomerates,which have already been waterproofed or are intended to be wateiproofed,the fireproofing solutions or components thereof should be adapted tothe compatible waterproofing agent.

As fireproofing agents, one preferably uses mixture of ammoniumphosphates or compounds capable of forming the same.

As waterproofing agents, one may use solutions or emulsions ofsubstances such as micro-cristalline waxes which are precipitated andattached to the agglomerates or the constituting element thereof bycausing the pH of the said emulsions or solutions to be modified in sucha manner as to give rise to a flocculation of the said emulsion or tothe precipitation of the compounds contained in the solution. Thismodification of the pH may be caused by the fireproofing saltsthemselves or by at least one of the compounds which are intended toform the said salts in situ.

The concentrations of the fireproofing salts or components thereofshould be such that they lead to the presence in situ of quantities of HPO comprised between about 5 and 15% by weight of the dry material whichis to be fireproofed. The concentration of the waterproofing solutionsor emulsions should be such that the quantity of dry waterproofingagent, fixed on the treated material is comprised between about 0.5 and5% by weight of dry material.

In certain cases, it may be advantageous to use solutions and/oremulsions containing an excess of the products which are to be finallyfixed on the agglomerates. The said solutions or emulsions are forced topass through the vessel of the material which is to be treated, e.g. byaspiration in vacuum vats, by atomizing or otherwise. Thereafter theunretained excess of product is recovered for future use, after apossible adjustment of the contents thereof in active material. Theoperation may be carried out in one or more successive steps andmaterials in a crude state or during the transformation or shapingthereof or on finished agglomerates. The application of the variousingredient solutions and/or emulsions, may be operated simultaneously orsuccessively. The said ingredient solutions and/or emulsions, may haveadded to them salts or other agents for giving to the various treatedmaterials special supplementary properties or features, e.g. fungicides,insecticides and the like. Whatever the process which is used and theorder which is adopted for the various operations it is essential thatthe various ingredients, solutions or emulsions, as Well as the addedsubstances, conform to the established conditions of compatibility. Themethod according to the invention therefore makes it possible if desiredto apply the solution or emulsion in closed circuit. There is thus noloss of active substances, the quantities of which formed and fixed onthe treated materials are determined, as concerns their homogeneouscontent and control distribution by the concentration of the circulatingsolutions or emulsions and by the number of cycles thereof. Furthermorea lesser quantity of active solution or emulsion may be used.

-- According to the invention, it istherefore possible:

(1) In the case of panels made of fibers and more particularlyinsulating panels:

(a) Either to operate a prior waterproofing of the fibers before theshaping into panels then, after the said shaping to operate thefireproofing by incorporating waterproofing solution throughout thetotal thickness of the panels;

(b) Or to first form the panels, then to waterproof and fireproof thesame, the said two operations being carried out independently in therequired conditions of compatibility and fixation by incorporatingthroughout the thickness of the panels the fireproofing andwaterproofing solutions and/or emulsions.

(0) Or to form the panels and then simultaneously waterproofing andfireproofing the same in the required conditions of compatibility andfixation by incorporating in the panels fireproofing and waterproofingsolution or emulsion.

(d) Or to operate the fireproofing on a finished panel, that is to sayon a panel which has been shaped and dried, the said panel having beenwaterproofed beforehand or not.

If the panels which is submitted to the fireproofing treatment has notbeen previously waterproofed, it is possible to incorporate thewaterproofing emulsion simul taneously with or independently of thefireproofing solution while conforming to the conditions of fixation.The panels are then finally subjected to a drying process.

(2) In the case of the treatment of particles, which are intended toform panels, to impregnate the said particles with the fireproofingsolution, before they are dried and waterproofing the same by addingwaterproofing .agent in the binding agent for the particles or toimpregnate simultaneously or successively the particles before they aredried, with a fireproofing solution and a waterproofing emulsion in therequired conditions of compatibility and fixation. Thequality of thewaterproofing material must be such that the further binding of theparticles by synthetic resins, more particularly urea-formaldehyderesins, is not disturbed.

In the said two cases for multiple layer panels, the particles in eachlayer should preferably be fireproofed and waterproofed in order toobtain a good result but diiferent proportions of the fireproofing andwaterproofing agents may be used in the different layers. It is evenpossible not to use the said product in certain layers.

Various embodiments of the method according to the invention aredescribed moreover by way of examples:

Example 1 Deal boards of 0.3 x 2.5 x 0.01 m. were immersed for 24 hoursin 5% ammonia solution. After a quick draining, the said boards wereimmersed in 20% ammonium phosphate solution having a pH of 3.95. Afterdrying, the said boards containing 10% by weight, of ammonium phosphateswere subjected to infiammability tests and proved to be fireproof.

Example 2 Oak floor boards of 0.4 x 0.7 x 0.05 m. were immersed for 12hours at room temperature in a 5% ammonia solution. After having beenquickly drained, the said boards were immersed during 12 hours in a 22%aqueous bath of ammonium phosphates having a pH value of 3.9, at atemperature of 65 C. After drying, the said boards containing 9.5% byweight of fireproofing salt were submitted to the standard tests andproved to be fireproof.

Example 3 Deal boards of 0.3 x 2.5 x 0.02 m. were immersed in water for24 hours, the said boards were then immersed for 12 hours in a 5%aqueous ammonia solution at 15 C. After draining, the boards were.immersed for 6 hours in a 20% solution of ammonium phosphate havingapI-I .valueof 5.95, the temperature being maintained at 80 C. Aftertdrying, the average of fireproofing salt contents of the boards was of8% by weight.

When subjected to inflammability tests, the boards proved to beditficult to burn.

Example 4 Beech plies of 2.1 mm. thick were immersed for 5 minutes in a5% ammonia solution, then, after draining, were immersed for the sametime in an ammonium phosphate solution having a specific gravity of 1.13and a pH value of 3.9, the said solution beingmaintained at atemperature of 35 C.

After drying in air at room temperature, the treated plies had absorbed11.1% by weight of fireproofing salts and proved to be non-inflammable.

Example 5 After being immersed for 15 minutes in a 5% aqueous ammoniasolution, beech plies of 2.1 mm. thick were immersed for the same timein the same ammonium phosphate solution as in Example 4 but thetemperature was maintained at 70 during the whole operation. Afterdrying at room temperature, it was found that the wood had absorbed10.3% by weight of fireproofing salts.

Example 6 The Example 4 was repeated with the difference that ammoniumfluoride was added to the phosphate solution, in a proportion of 45g./l. solution.

Bacteriological tests showed that no micro-organisms developed on thetreated plies which had the same degree of fireproofing.

Example 7 1 mm. thick plies of Aucoumea klayneiana were immersed inwater until they had absorbed 80% by weight or" water. The plies werethen immediately subjected to a first immersion for minutes in a 5%ammonia solution, then after a quick draining, to a second immersion forthe same time in a solution of an ammonium phosphate having a pH valueof 3.9 and a P0,; ions content of 18%, the temperature of which wasmaintained at 65 C. The plies were then dried in a drying apparatus inwhich air was admitted at a temperature comprised between 130 and 150 C.After minutes in the drying apparatus, the wood contained 10% water byweight. The shape of the plies was not modified and the surface thereofhad retained its initial aspect. They contained 12.2% of fireproofingsalts and their pH value was 6.6.

Three-ply wood panels obtained with the above mentioned plies weresubmitted to standard inflammability test and proved completelyfireproof.

Example 8 Example 7 was repeated with the only difference that 0.5% byweight of pentachlorophenol was added to the ammonia solution.

The fireproofed plies were submitted to bacteriological tests whichshowed that no micro-organisms developed therein.

Example 9 8 kg. of a 50% aqueous emulsion of an inorganicmicro-crystalline wax were added to 10 m? of lignocellulosic fiber pastecontaining g./l. of dry material and the pH of which was brought between8.5 and 9 by careful addition of an expanding ammonia solution and thewax was precipitated on the fibers by adding a strong mineral acid untilthe pH value of the mixture reached 5.5. The paste was then formed intopanels and the said panels were placed on the band of a suction filterand sprinkled with a solution of ammonium phosphate containing 55 kg./m.of phosphoric acid and having a pH value comprised between 5.5 and 6.

When the volume of phosphate solution having passed through the filter,reached the panels, the sprinkling was stopped and the panels werequickly drained. The phosphate solution which had passed through thepanels was recovered and used for a further impregnation after addingphosphoric acid and adjusting the pH thereof at the above indicatedvalues. Samples taken from the panels showed that the absorption offireproofing salts was acceptable. The panels proved to be fireproof.

Example 10 Fiber panels were prepared according to conventional methodsand dried in a drying apparatus.

The said panels were then placed on a vacuum vat and uniformlyimpregnated with a solution of ammonium phosphate having a pH value of 6and titrating g./l. of phosphoric acid to which had been incorporated 5kg./m. of non-ionic micro-crystalline wax emulsified in water. Theexcess solution having passed through the panels was recovered and usedfor a further impregnation operation after readjusting the contents ofthe various ingredients. After drying the panels during which waxparticles were fixed on the fibers, the panels contained 10% by weightof phosphoric acid in the form of ammonium phosphate.

Samples taken from the panels showed that the absorption was acceptableand the panels were fireproof.

Example 11 100 kg. of cut flax stalks were placed in a rotating cylinderin which they were successively impregnated by spraying:

(1) 65 l. of an expanding ammonia solution containing 15 g./l. of NH (2)65 l. of orthophosphoric acid solution containing 102 g./l. of H PO Thecut stalks were then dried and made into a pulp with a synthetic resincontaining 2% based on weight of the stalks, of the micro-crystallinewax.

The pulped material was shaped into panels by the conventional method.The said panels contained 10% by weight of H PO in the form of ammoniumphosphate. The standard tests showed that the said panels werefireproof.

Instead of operating discontinuously in the rotating cylinder, it isalso possible to operate continuously by using a continuous pulpingmachine of known type in which the first sprayers are fed with theammonia solution and the following sprayers are fed with the phosphoricsolution, the rate of feed being adjusted in order to correspond to thequantity of solution specified in Example 11.

What we claim is:

1. A rapid process for fireproofing cellulose and lignocellulosematerial, which comprises impregnating said material with an aqueoussolution of ammonia ina concentration and for a period of timesuflicient to expand the channels and cells in the material and topermit the penetration into said material of a desired quantity ofammonium ions but insuificient to alter the fibers thereof; andthereafter causing phosphoric ions to penetrate into said material bycontacting said material with an aqueous solution containingorthophosphoric acid ions in a concentration and for a period of timesufiicient for the phosphoric ions to combine with said ammonium ionspresent in said material to form in situ at the time of drying anammonium phosphate uniformly distributed throughout said material whilegiving said material a. pH value that does not alter its initialmechanical and surface properties.

2. A process as defined in claim 1, in which said solution containingsaid orthophosphoric ions also contains ammonium ions in a quantityfixed by the ratio of the quantity of ammonium ions already contained insaid cellulose or lignocellulose material to the quantity oforthophosphoric ions carried into said material in said solution.

3. A process for fireproofing cellulose and lignocellulose material,which comprises impregnating said material with an aqueoussolution ofammonia in a concentration and for a period of time sufficient to expandthe channels and cells in the material but insufficient to alter thefibers thereof and thereafter impregnating the material with an aqueoussolution of an ammonium hydrogen phosphate in a concentration and for aperiod of time suflicient to react with said ammonia and thereby form anammonium phosphate in situ throughout the material and provide a pHbetween 6.3 and 7.4.

4. A process for fireproofing cellulose and lignocellulose material,which comprises impregnating said material with an aqueous solution ofammonia in a "concentration and for a period of time suflicient toexpand the channels and cells in the material but insufiicient to alterthe fibers thereof and thereafter impregnating the material with anexcess of an aqueous solution of an ammonium hydrogen phosphate in aconcentration and for a period of time 'sufiicient to react with saidammoniaand form in situ at the time of drying an ammonium phosphateuniformly distributed throughout said materialwhile giving said materiala pH value that does not alter its initial mechanical and surfaceproperties, and removing the excess of said ammonium phosphate solutionafter said in situ reaction has taken place.

5. A process for fireproofing cellulose and ligncellulose material,which comprises impregnating said material with a 3-10% aqueous solutionof ammonia fora period of time sufiicient to expand the channels andcells in the material but insuflicient to alter the fibers thereof andthereafter impregnating the material with a --30% aqueous solution of anammonium hydrogen phosphate for a period of time sufiicient to reactwith said ammonia and form in situ at the time of drying am ammoniumphosphate uniformly distributed throughout said material while givingsaid material a pH value that does not alter its initial mechanical andsurface properties.

6. A process for fireproofing cellulose and lignocellulose material,which comprises impregnating said material with an aqueous solution ofammonia in a concentration and for a period of time suflicient toexpand-the channels and cells in the material but insuflicient to alterthe fibers thereof and thereafter impregnating the material with anaqueous solution of an ammonium hydrogen'phosphate having a pH between 3and 7 in -aconcentration and for a period of time sufficient to reactwith said ammonia and form in situ at the time ofdrying an ammoniumphosphate uniformly distributed throughout said material while givingsaid material -a pH value that does not alter its initial mechanical andsurface properties.

7. A process for fireproofing cellulose and lignocellulose material,which comprises impregnating said material with an aqueous solution ofammonia in a concentration and for a period of time sufiicient to expandthe channels and cells in the material but insufiicient to alter thefibers thereof and thereafter impregnating the material with an aqueoussolution of an ammonium hydrogen phosphate in a concentration and for aperiod of time sufficient to react with said ammonia and form in situ atthe time of drying an ammonium phosphate uniformly distributedthroughout said material while giving said material a pH value that doesnot. alter its initial mechanical and surface properties, and continuingsaid reaction until the amount of ammonium phosphate fixed on saidmaterial is equivalent to 5 to of phosphoric acid based on the dryweight of the material. I

8. A process for fireproofing and waterproofing cellulose andlignocellulose material, which comprises impregnating said material withan aqueous solution of ammonia in a concentration and for a period oftime sufficient to expand the channels and cells in the material butinsuflicient to alter the fibers thereof and thereafter impregnating thematerial with an aqueous solution containing phosphoric acid ions in aconcentration and for a period of time suflicient to react with saidammonia and form in situ at the time of drying an ammonium phosphateuniformly distributed throughout said material while giving saidmaterial a pH value that does not alter its initial mechanical andsurface properties, and providing together with one of said aqueoussolutions an aqueous dispersion of a waterproofing agent dispersibletherein under its pH conditions.

9. The process of claim 8 in which both the ammonium phosphate solutionand the aqueous dispersion of the waterproofing agent are used in excessand in which said excess thereof are removed after said in situ reactionhas taken place.

10. A process for fireproofing and waterproofing cellulose andlignocellulose material, which comprises impregnating said material withan aqueous solution of ammonia in a concentration and for a period oftime sufficient to expand the channels and cells in the material butinsufiicient to alter the fibers thereof and thereafter impregnating'thematerial with an aqueous solution containing phosphoric acid ions in aconcentration and for a period of time sufiicientto react with saidammonia and form in situ at the time of drying an ammonium phosphateuniformly distributed throughout said material while giving saidmaterial a pH value that does not alter its initial mechanical andsurface properties, and providing with one of said aqueous solutions anaqueous emulsion of a microcrystalline Wax stable in said solution underits pH conditions.

11. A process for fireproofing and waterproofing cellulose andlignocellulose material, which comprises impregnating said material withan aqueous solution of ammonia in a concentration and for a period oftime sufficient to expand the channels and cells in the material butinsufficient to alter the fibers thereof and thereafter impregnating thematerial with an aqueous solution containing phosphoric acid ions in aconcentration and for a period of time sufiicient to react with saidammonia and form in situ at the time of drying an ammonium phosphateuniformly distributed throughout said material While giving saidmaterial a pH value that does not alter its initial mechanical andsurface properties, and providing together with one of said aqueoussolutions an aqueous dispersion of a waterproofing agent dispersibletherein under its pH conditions and in a concentration sufi'icient toimpregnate said material with 0.5 to 5% of its dry weight ofwaterproofing agent.

References Cited in the file of this patent UNITED STATES PATENTS761,870 Baxter June 7, 1904 1,422,242 Valls July 11, 1922 1,942,977Payne Jan. 9, 1934 1,945,714 Winogradow Feb. 6, 1934 2,698,816 Dosmannet al. Jan. 4, 1955 2,766,139 Green et a1. Oct. 9, 1956 2,868,673 Depewet al. Jan. 13, 1959 2,930,106 Wrotnowski Mar. 29, 1960 FOREIGN PATENTS440,026 Great Britain Dec. 16, 1935

1. A RAPID PROCESS FOR FIREPROOFING CELLULOSE AND LIGNOCELLULOSEMATERIAL, WHICH COMPRISES IMPREGNATING SAID MATERIAL WITH AN AQUEOUSSOLUTION OF AMMONIA IN A CONCENTRATION AND FOR A PERIOD OF TIMESUFFICIENT TO EXPAND THE CHANNELS AND CELLS IN THE MATERIAL AND TOPERMIT THE PENETRATION INTO SAID MATERIAL OF A DESIRED QUANTITY OFAMMONIUM IONS BUT INSUFFICIENT TO ALTER THE FIBERS THEREOF: ANDTHEREAFTER CAUSING PHOSPHORIC IONS TO PENETRATE INTO SAID MATERIAL BYCONTACTING SAID MATERIAL WITH AN AQUEOUS SOLUTION CONTAININGORTHOPHOSPHORIC ACID IONS IN A CONCENTRATION AND FOR A PERIOD OF TIMESUFFICIENT FOR THE PHOSPHORIC IONS TO COMBINE WITH SAID AMMONIUM IONSPRESENT IN SAID MATERIAL TO FORM IN SITU AT THE TIME OF DRYING ANAMMONIUM PHOSPHATE UNIFORMLY DISTRIBUTED THROUGHOUT SAID MATERIAL WHILEGIVING SAID MATERIAL A PH VALUE THAT DOES NOT ALTER ITS INITIALMECHANICAL AND SURFACE PROPERTIES.